The present invention relates to a device for folding and sealing the head of a folded carton made out of a web or blank of cardboard coated on the inside with a thermoplastic layer in a folding and pressure-welding station that has folding and pressure-welding tools consisting of a pair of jaws that can be brought together like tongs, one jaw mounted on a pivoting lever and the other mounted along with a welding element that operates in conjunction with the first jaw on a common support that is suspended in such a way that it can pivot.
A device of this kind is known, from U.S. Pat. No. 4,241,560 for example. This known device for folding and sealing the head of a folded carton has a common drive mechanism in the form of a pivoting radial cam that controls both the folding tools and the pressure-welding tools. The folding and pressure-welding motions and introduction of forces are transmitted by pressure-application rollers resting against the outer contour of the cam to the folding and pressure tools. The common drive mechanism for the folding and pressure-welding necessitates positioning the drive and control elements essentially above the folded cartons, which are advanced discontinuously on a conveyor belt. The mechanical drive and control elements above the folded cartons, which are opened or which are to be sealed, make it difficult to ensure that the inner surface of the still open cartons do not get contaminated with residual product because many points are necessarily difficult to access for cleaning. Furthermore, since the common drive mechanism for the folding and pressure tools makes it impossible to design the motions of the tools to be independent, the mutual position of the pressure tools will alter even when very slight wear occurs, on the force-transmission rollers for example, which has a detrimental effect on the quality of the welded seam. Futhermore, in the particular concept of the known device, both the shaft that bears the common cam and another shaft that bears the arms carrying the lever and support are very powerfully stressed while pressure is being applied, which is a particular drawback when several webs are involved.